Not Populated but included in simulation

Schematic Simulation (Ngspice)
1

This is not so much a question as it is an observation.

In schematic it is possible to clearly mark components as “Not Populated”. When they are NP, they are clearly marked by an “X” in the schematic.

It is also possible to include or exclude components from a simulation, but there is no visible indication of this in the schematic.

It is very natural to think that components that are NP, are NOT included in the simulation, but that is not the case.
Components that are NP are not automatically excluded from simulations. Is there a use case for this?

-Would it be more natural to exclude NP components from simulations automatically?

2

I do see where you’re coming from, but I immediately worry about KiCad being clever and causing grief by making assumption about user intent. My thinking is:

  • We need separate toggles for DNP and Not in Simulation (they are independent settings, most connectors are unlikely to be simulated but will be placed for instance)
  • Automatically switching another checkbox based on the result of another in the same section feels weird, inconsistent with how checkboxes normally work
  • Alternatively, KiCad could quietly OR the checkboxes in the background for the purpose of Not in Simulation. This would be the secret cleverness that I worry about… Very confusing for a new (and maybe existing) users

All that being said, I really can’t come up with a counter example for something that should be DNP but in simulation.

3

The term “Do not Populate”, not “Not Populated” is an assembly instruction for component placement in a PCB assembly.

“Simulation” uses mathematical models to replicate behavior of electronic devices or circuits, so excluding from simulation means not to be simulated.

These functions often have very little bearing on each other.

4

A socket mounted IC?
A screw connected antenna?
A panel mounted fuse or on/off switch or potentiometer?
Large, heatsinked transistors that need to be mechanically mounted and later hand soldered in place?

Let your imagination run wild @scandey :smiley:

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5

Hi @jmk @scandey

The main point is that it is that when you are making a simulation it is not possible to see which components are included in the simulation, and which are not. You have to mouse click on each component individually to see if it has a checkmark the right place. And that also apply to the DNP components. But maybe that is less of a problem.

I understand the point of @scandey that you don’t want KiCad to be clever.

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6

There is a request to fix this at Visual indication of "Exclude from Simulation" in schematic (#15382) · Issues · KiCad / KiCad Source Code / kicad · GitLab. You might give it a “Thumbs Up”.

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